chore(docs): retire dead fable-mcp wheel-distribution refs; untrack docs/superpowers

The old standalone fable-mcp wheel/download flow is gone from code (no route,
no Dockerfile build, no FABLE_MCP_DIST_DIR). Update api-keys-and-mcp,
api-reference, architecture, configuration, development to describe the
in-app HTTP MCP at /mcp (Bearer auth). Untrack the 18 committed
docs/superpowers/ files so the existing .gitignore takes effect.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/development.md

@@ -164,7 +164,7 @@ Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
 ```
 
 Types: `feat`, `fix`, `refactor`, `docs`, `chore`, `test`
-Scopes: feature area (e.g. `chat`, `briefing`, `fable-mcp`, `notes`)
+Scopes: feature area (e.g. `chat`, `journal`, `mcp`, `notes`)
 
 ## Testing